Chapter 8 - Reactivity trends (MODULE 3)

Question 1

What is the alternate name for group 2 metals

Answer 1

alkaline earth metals

Question 2

How many outer shell electrons do group 2 elements have and what subshell are they in

Answer 2

2 electrons, s subshell

Question 3

What type of agents are group 2 metals and why

Answer 3

reducing agents because they reduce other species

Question 4

What is the general reaction of group 2 metal, M, and Oxygen

Answer 4

2M + O2 -> 2MO

Question 5

What is the general equation for the reaction of a group 2 metal, M, with water

Answer 5

M + 2H2O -> M(OH)2 + H2

Question 6

how do the reactions of group 2 metals with water compare down the group

Answer 6

gets more vigorous down the group

Question 7

what is the equation for the reaction of a metal with a dilute acid

Answer 7

Metal + acid -> salt + hydrogen

Question 8

Why do the ionisation energies of group 2 metals decrease down the group

Answer 8

more electron shielding, greater nuclear charge, less nuclear attraction, easier to lose electrons

Question 9

why do group 2 metals get more reactive down the group

Answer 9

they react by losing electrons and ionisation energies are lower so this is easier

Question 10

how does the pH and water solubility of group 2 hydroxides compare down the group

Answer 10

pH -> more alkaline
water solubility -> more solublw

Question 11

How is calcium hydroxide used in agriculture

Answer 11

used to neutralise acidic soil

Question 12

how are group 2 metals often used in medicine

Answer 12

used as antacids for treating acid indigestion (helps neutralise HCl in stomach )

Question 13

Which group is the most reactive of the non metals

Answer 13

halogens

Question 14

how and why do the halogens differ in boiling points

Answer 14

more electrons down the group, so stronger London forces and more energy needed to break them, so higher boiling point

Question 15

how do halogens exist at RTP

Answer 15

diatomic molecules, all 3 states depending on which halogen

Question 16

What is the electron configuration of the outer shell of halogens

Answer 16

s2 p5

Question 17

What type of agents are halogens and why

Answer 17

oxidising agents because upon reacting with a halogen, other species are reduced

Question 18

When do halogen - halide displacement reactions occur

Answer 18

when halogen is more reactive than halide

Question 19

what is the order of reactivity of the first four halogens

Answer 19

fluorine, chlorine, bromine, iodine

Question 20

what are the colours of Cl2, Br2 and I2 upon dissolving with water

Answer 20

pale green, orange and brown

Question 21

What are the colours of Cl2, Br2 and I2 upon dissolving in cyclohexane

Answer 21

pale green, orange, violet

Question 22

Is there a reaction between Cl2 and

• Cl-
• Br-
• I-

Answer 22

• no reaction
• yes
• yes

Question 23

Is there a reaction between Br2 and

• Cl-
• Br-
• I-

Answer 23

• no reaction
• no reaction
• yes

Question 24

Is there a reaction between I2 and

• Cl-
• Br-
• I-

Answer 24

• no reaction
• no reaction
• no reaction

Question 25

how reactive is fluorine compared to the other halogens

Answer 25

extremely reactive - reacts with almost everything it comes in contact with

Question 26

Why is astatine so rare

Answer 26

it is radioactive and rapidly decays

Question 27

why does the reactivity of halogens decrease down the group

Answer 27

atomic radius increases, more shielding from inner shells, less nuclear attraction and so harder to gain an electron, reactivity decreases

Question 28

What is disproportionation

Answer 28

a redox reaction in which the same element is both oxidised and reduced

Question 29

What special type of reaction is chlorine with water - what is the equation for this

Answer 29

disproportionation - Cl2 + H2O -> HClO + HCl

Question 30

What special type of reaction is chlorine with sodium hydroxide - write an equation for this

Answer 30

disproportionation - Cl2 + 2NaOH -> NaClO + NaCl + H2O

Question 31

what are the risks of using chlorine (3)

Answer 31

- it is extremely toxic and - is a respiratory irritant. Can be fatal in large concentrations - often forms chlorinated hydrocarbons which are cancerous

Question 32

What are the benefits of adding chlorine to water before drinking

Answer 32

purifies the water from harmful microbes

Question 33

What is qualitative analysis

Answer 33

analysis relying on observations rather than measurements

Question 34

What is the carbonate test - what is the observation - what is the additional test to confirm

Answer 34

add acid - effervescence - bubble through limewater, will turn cloudy if carbonate was present

Question 35

What is the sulfate test - what is the observation

Answer 35

add Barium Nitrate and Nitric acid - white precipitate forms

Question 36

What is the initial halide test - what are the observations

Answer 36

add silver nitrate and nitric acid - chloride: white ppt - bromide: cream ppt iodide: yellow ppt

Question 37

what is the second test that can be done for identifying halide ions - what are the observations

Answer 37

add NH3 - chloride soluble in dilute NH3 - bromide soluble in concentrated NH3 - iodine insoluble

Question 38

What is the sequence of tests for anions

Answer 38

carbonate - sulfate - halides

Question 39

If there is a mixture of anions in a solution, how do you test for all of them

Answer 39

1. carbonate test - keep adding dilute HNO3 until effervescence stops 2. sulfate test - add an excess of Ba(NO3)2 and filter it out after 3. perform halide test using AgNO3 and NH3

Question 40

What is the test for ammonium ions - what is the positive observation - why does this work

Answer 40

heat together solution with aqueous hydroxide ions add test with moist indicator paper - paper turns blue - initial reaction forms ammonia, which is highly alkaline